Crystalline structure of an ammonia borane–polyethylene oxide cocrystal: a material investigated for its hydrogen storage potential

Abstract

The crystalline structure of a cocrystal comprising ammonia borane (AB) and a short-chain polyethylene oxide (PEO or PEG) has been determined by single-crystal X-ray diffraction. The components interact via hydrogen bonds between each of the hydrogen atoms at the NH 3 end of the AB molecules and alternate oxygen atoms along the PEO backbone. The PEO chains in the structure exhibit an unusual conformation where their curvature reverses every 5 monomers, such that the polymer snakes through the crystal. This is the first time that an AB composite material has been determined to be a cocrystal, and no structure determination of a cocrystal to confine AB has been reported before.

Tetraglymes as Prochiral Host Reagents for Ammonia Borane

“…The pseudo‐cyclic conformer is stabilized by the system of hydrogen bonds between the guest AB molecules and the tetraglyme molecule. Quite recently, a co‐crystal of the short‐chain polyethylene glycol (PEG) and AB was reported . It comprises (CH 2 CH 2 O) 5 · AB patterns similar to the 1· (AB) 2 complex.…”

“…Quite recently, a co‐crystal of the short‐chain polyethylene glycol (PEG) and AB was reported . It comprises (CH 2 CH 2 O) 5 · AB patterns similar to the 1· (AB) 2 complex. As 1· (AB) 2 , complexes of crown‐ethers and PEG with AB have similar structural patterns, they are worth to be compared.…”

Recent Development in Nanoconfined Hydrides for Energy Storage

“…Attempts to restrict oxygen and moisture exposure of active hydrogenation sites in hydride materials have been made through the engineered approach of covering the hydride materials with a layer of H 2 -permeable polymer [88,127,156,[173][174][175]. This approach proved to be very successful, provided that the hydride coverage was indeed complete (Table 6).…”

“…NaBH4 [49,74,216,236,241], Mg(BH4)2 [42,55,61,70,105,126,132,151,159,207,216,220,224,236,242,243], Ca(BH4)2 [116,216,236,243] and (TM)(BH4)x [150,216], ammonia-borane NH3.BH3 [36,38,63,64,75,85,86,88,90,139,[140][141][142][143][144]153,154,156,162,171,175,197,213,[244]…”

A novel ammonium pentaborate – poly(ethylene-glycol) templated polymer-inclusion compound

“…There has been much interest in the use of polymers to template materials such as zeolites, metal organic frameworks (MOFs), and even organic co-crystals. The polymer may form an intrinsic part of a co-crystal structure 1 or it may simply act as a template for crystal growth in the synthesis of new polymorphs. 2 Alternatively, the polymer may act as a template for the formation of novel supramolecular structures.…”